7804

• UCREFRP Catalog Number: 7804
• Author: Hagan, H. K. and J. E. Banks.
• Title: An Ecological And Limnological Study of the Green River in Dinosaur National Monument.
• USFW Year: 1963.
• USFW - Doc Type: \
• Copyright Material: NO

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to re-inventory' the study sections. Beaver Creek and Browns Park stations
were deleted when it lias found that there were no fish at the Lodore col-
lecting station. The fact that pollution occurred in the Green Siver just
prior to this sampling date bad nothing to do with the size at the group
or the intensity of the sampling except that a much greater effort had to
be made in 1962 to collect fish despite the fact that water conditions
then were much better for collecting that they were in 1961.

Fishes and ,fish stomach samples collected during the summer by t-lr.
Banks and those taken in October, were transported to Colorado State
university for study and analysis. Representative fishes have been made
available to the museum at Dinosaur National M:mument as part of the
contract obligation.

Because the aquatic insects were investigated in detail by Utah
Scientists they were regarded in the report lugely in a quantitative
measure or in regard to their appearance in the food of the fishes.

Results

Summer investigations
Physical conditions (general)

A maJor effort was made to correlate the abundance of the several.
fish species with the type ot stream bottom and the velocity ot the current.
High vaters and limited access made this difficult to accomplish. Typical
canyon habitat as viewed tromHa.rpers Corner (Figure 1) shows how the
heavy sediment load of the stream 18 depos ited as the water level drops.
Strips of hard pressed sands and gravels and silt are exposed along the
edges ot the slowing Yaters. The steep canyon wall.s tend to deflect the
currents back and forth forming pools, eddies and backwaters as sanctuaries
for tish. Sediments accumulate on the inner slow water sides of the curves
wh1l.ethe oute]:' 8.l'eas are frequently scoured and abraded to the bare rock
by thesvUt current. Although the river would appear untenable for fish
in ~ sections and at certain seasons, these limited niches at backwaters
and eddies are populated at all seasons ll'ith a variety of fishes. For~1n&
for food is doubtlessly limited during the high waters and this limita-
tion appears in the correlating wide variances in growth rings on the
scales ot the fish. There is an interesting possibility that scales ot
fishes tram fast and slower sections can be used to interpret something
at their little known life history.

Var1ation in stream grade is considerable in the ~nument area. In
the vic1n1:ty 01' Lodore the rate of fall is approximately 2.5 feet per mile.
In t128 lAdore Canyon the average grade increases to 18.2 feet per mile
and theDslows to approximately 4 teet of drop as the river accepts the
waters 0'1 the Yampa at Echo Park. In l1hirlpaol Canyon (Fiaure 1) the grade
increases again to more than 12 feet of drop permlle. In Island Park and
Rainbow Park the grade is only 3.3 feet per mile but. as the river plunges
through the last barrier of Split MJuntain Canyon it takes it maximum
drop with an average of ne81'ly 22 feet per mile. In these st.airstep
increases and decreases in grade, the change in habitat is considerable

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